Decreased Hysteresis Benefited from Enhanced Lattice Oxygen and Promoted Band Alignment with Electron Transport Layer Modification in Perovskite Solar Cells

SnO₂ electron transport layer (ETL) morphology plays a vital role in carrier transportation and the properties of perovskite solar cells (PSCs). However, the uneven and pore surface would inevitably lead to high interface defects, high hysteresis, and poor performance. In this work, we use a molecular modifier 4-guanidinobenzoic acid methanesulfonate (GAMSA) to build a molecular bridge on the buried interface of SnO₂/perovskite. XPS results demonstrate that the ratio of lattice oxygen (O_L)/adsorbed oxygen (O_V) increased from 1.35 to 2.34 after GAMSA modification, thus, Sn⁴⁺ and O vacancy defects in SnO₂ were effectively reduced. Meanwhile, the conduction band minimum of the ETL enhanced from -4.33 eV to -4.07 eV, which obviously facilitated the electron transport. As a result, the optimal device exhibits an enhanced efficiency of 22.42%, which is much higher than that of the control one of 20.13%, with a greatly decreased hysteresis index from 14.35% to 3.27%. Notably, the optimized target device demonstrated excellent long-term stability, maintaining an initial efficiency of 87% after 2000 h storage in a N₂ atmosphere in the dark at room temperature. This work paves a new method of ETL modification to improve lattice oxygen of SnO₂ and restrain hysteresis for the enhanced performance of PSCs.